The invention relates to rolling mills for sheet material normally in the form of a continuous band or web, in which two work rolls define a nip between which the material to be processed is guided. Such mills also usually include one or more back-up rolls associated with each work roll. In mills of the type to which the present invention relates, the plane containing the axes of the work rolls is offset relative to the plane containing the axes of the back-up rolls, and the work rolls are supported against the direction of offset from the back up rolls.
Rolling mills of this kind, which are described for example in U.S. Pat. No. 4,059,976, have considerable advantages over the usual four-high arrangement wherein the axes of the work rolls and of the back-up rolls are situated in one vertical plane, particularly when thin metal sheeting is being rolled, such as thin aluminium foils. Where the foil thickness is for example 0.1 mm, owing to the elasticity of the system it is impossible, when deflection of the rolls occurs, to apply working pressure of a specific quality uniformly over the entirety of the roll gap. Supporting devices can counteract the elastic deflection phenomena of the roll system. In one known construction; e.g., in rolling mills produced under the name MKW (multipurpose cold rolling mill) by the German firm of Schloemann Siemag AG., a system of bearing rolls is provided which accepts the load of the work roll in the horizontal direction and with which the deflections of the work roll in the horizontal direction can also be corrected. In certain cases this can be done by preloading or by convexing the rolls.
Rolling mills of this kind are operable in both possible rolling directions, in each case by reversal of the direction of rotation of the rolls. But the circumstances and the components of force vary in the respective individual rolling or rotation directions, so that the rolling mill has to be suitably adaptable or adjustable to the particular rolling programme to be carried out; i.e., both when changing the rolling direction and also when making corrections during a pass. With present-day rolling mills, problems arise more particularly in connection with such supporting devices and their adjustability. Mechanical friction occurs between the component parts, and such friction phenomena vary with the forces applied. Further, marking can develop, of which traces may be reproduced as far as on to the often highly polished rolling surfaces of the work rolls. Thus work rolls supported by such mechanisms are subject to additional wear.